<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        ul li{
            position: relative;
            float:left;
            width: 150px;
            height: 200px;
            border: 1px solid blue;
            list-style: none;
            margin-left: -1px;
        }
        ul li:hover{
            z-index: 1;
            border: 1px solid #ff6700;
        }
    </style>
</head>
<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
    </ul>
</body>
</html>